drivers/i2c/busses/i2c-bcm2835.c

   1 /*
   2  * BCM2835 master mode driver
   3  *
   4  * This software is licensed under the terms of the GNU General Public
   5  * License version 2, as published by the Free Software Foundation, and
   6  * may be copied, distributed, and modified under those terms.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  */
  13
  14 #include <linux/clk.h>
  15 #include <linux/completion.h>
  16 #include <linux/err.h>
  17 #include <linux/i2c.h>
  18 #include <linux/interrupt.h>
  19 #include <linux/io.h>
  20 #include <linux/module.h>
  21 #include <linux/platform_device.h>
  22 #include <linux/slab.h>
  23
  24 #define BCM2835_I2C_C           0x0
  25 #define BCM2835_I2C_S           0x4
  26 #define BCM2835_I2C_DLEN        0x8
  27 #define BCM2835_I2C_A           0xc
  28 #define BCM2835_I2C_FIFO        0x10
  29 #define BCM2835_I2C_DIV         0x14
  30 #define BCM2835_I2C_DEL         0x18
  31 #define BCM2835_I2C_CLKT        0x1c
  32
  33 #define BCM2835_I2C_C_READ      BIT(0)
  34 #define BCM2835_I2C_C_CLEAR     BIT(4) /* bits 4 and 5 both clear */
  35 #define BCM2835_I2C_C_ST        BIT(7)
  36 #define BCM2835_I2C_C_INTD      BIT(8)
  37 #define BCM2835_I2C_C_INTT      BIT(9)
  38 #define BCM2835_I2C_C_INTR      BIT(10)
  39 #define BCM2835_I2C_C_I2CEN     BIT(15)
  40
  41 #define BCM2835_I2C_S_TA        BIT(0)
  42 #define BCM2835_I2C_S_DONE      BIT(1)
  43 #define BCM2835_I2C_S_TXW       BIT(2)
  44 #define BCM2835_I2C_S_RXR       BIT(3)
  45 #define BCM2835_I2C_S_TXD       BIT(4)
  46 #define BCM2835_I2C_S_RXD       BIT(5)
  47 #define BCM2835_I2C_S_TXE       BIT(6)
  48 #define BCM2835_I2C_S_RXF       BIT(7)
  49 #define BCM2835_I2C_S_ERR       BIT(8)
  50 #define BCM2835_I2C_S_CLKT      BIT(9)
  51 #define BCM2835_I2C_S_LEN       BIT(10) /* Fake bit for SW error reporting */
  52
  53 #define BCM2835_I2C_BITMSK_S    0x03FF
  54
  55 #define BCM2835_I2C_CDIV_MIN    0x0002
  56 #define BCM2835_I2C_CDIV_MAX    0xFFFE
  57
  58 #define BCM2835_I2C_TIMEOUT (msecs_to_jiffies(1000))
  59
  60 struct bcm2835_i2c_dev {
  61         struct device *dev;
  62         void __iomem *regs;
  63         struct clk *clk;
  64         int irq;
  65         struct i2c_adapter adapter;
  66         struct completion completion;
  67         u32 msg_err;
  68         u8 *msg_buf;
  69         size_t msg_buf_remaining;
  70 };
  71
  72 static inline void bcm2835_i2c_writel(struct bcm2835_i2c_dev *i2c_dev,
  73                                       u32 reg, u32 val)
  74 {
  75         writel(val, i2c_dev->regs + reg);
  76 }
  77
  78 static inline u32 bcm2835_i2c_readl(struct bcm2835_i2c_dev *i2c_dev, u32 reg)
  79 {
  80         return readl(i2c_dev->regs + reg);
  81 }
  82
  83 static void bcm2835_fill_txfifo(struct bcm2835_i2c_dev *i2c_dev)
  84 {
  85         u32 val;
  86
  87         while (i2c_dev->msg_buf_remaining) {
  88                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
  89                 if (!(val & BCM2835_I2C_S_TXD))
  90                         break;
  91                 bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_FIFO,
  92                                    *i2c_dev->msg_buf);
  93                 i2c_dev->msg_buf++;
  94                 i2c_dev->msg_buf_remaining--;
  95         }
  96 }
  97
  98 static void bcm2835_drain_rxfifo(struct bcm2835_i2c_dev *i2c_dev)
  99 {
 100         u32 val;
 101
 102         while (i2c_dev->msg_buf_remaining) {
 103                 val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 104                 if (!(val & BCM2835_I2C_S_RXD))
 105                         break;
 106                 *i2c_dev->msg_buf = bcm2835_i2c_readl(i2c_dev,
 107                                                       BCM2835_I2C_FIFO);
 108                 i2c_dev->msg_buf++;
 109                 i2c_dev->msg_buf_remaining--;
 110         }
 111 }
 112
 113 static irqreturn_t bcm2835_i2c_isr(int this_irq, void *data)
 114 {
 115         struct bcm2835_i2c_dev *i2c_dev = data;
 116         u32 val, err;
 117
 118         val = bcm2835_i2c_readl(i2c_dev, BCM2835_I2C_S);
 119         val &= BCM2835_I2C_BITMSK_S;
 120         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_S, val);
 121
 122         err = val & (BCM2835_I2C_S_CLKT | BCM2835_I2C_S_ERR);
 123         if (err) {
 124                 i2c_dev->msg_err = err;
 125                 complete(&i2c_dev->completion);
 126                 return IRQ_HANDLED;
 127         }
 128
 129         if (val & BCM2835_I2C_S_RXD) {
 130                 bcm2835_drain_rxfifo(i2c_dev);
 131                 if (!(val & BCM2835_I2C_S_DONE))
 132                         return IRQ_HANDLED;
 133         }
 134
 135         if (val & BCM2835_I2C_S_DONE) {
 136                 if (i2c_dev->msg_buf_remaining)
 137                         i2c_dev->msg_err = BCM2835_I2C_S_LEN;
 138                 else
 139                         i2c_dev->msg_err = 0;
 140                 complete(&i2c_dev->completion);
 141                 return IRQ_HANDLED;
 142         }
 143
 144         if (val & BCM2835_I2C_S_TXD) {
 145                 bcm2835_fill_txfifo(i2c_dev);
 146                 return IRQ_HANDLED;
 147         }
 148
 149         return IRQ_NONE;
 150 }
 151
 152 static int bcm2835_i2c_xfer_msg(struct bcm2835_i2c_dev *i2c_dev,
 153                                 struct i2c_msg *msg)
 154 {
 155         u32 c;
 156         unsigned long time_left;
 157
 158         i2c_dev->msg_buf = msg->buf;
 159         i2c_dev->msg_buf_remaining = msg->len;
 160         reinit_completion(&i2c_dev->completion);
 161
 162         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
 163
 164         if (msg->flags & I2C_M_RD) {
 165                 c = BCM2835_I2C_C_READ | BCM2835_I2C_C_INTR;
 166         } else {
 167                 c = BCM2835_I2C_C_INTT;
 168                 bcm2835_fill_txfifo(i2c_dev);
 169         }
 170         c |= BCM2835_I2C_C_ST | BCM2835_I2C_C_INTD | BCM2835_I2C_C_I2CEN;
 171
 172         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_A, msg->addr);
 173         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DLEN, msg->len);
 174         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, c);
 175
 176         time_left = wait_for_completion_timeout(&i2c_dev->completion,
 177                                                 BCM2835_I2C_TIMEOUT);
 178         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, BCM2835_I2C_C_CLEAR);
 179         if (!time_left) {
 180                 dev_err(i2c_dev->dev, "i2c transfer timed out\n");
 181                 return -ETIMEDOUT;
 182         }
 183
 184         if (likely(!i2c_dev->msg_err))
 185                 return 0;
 186
 187         if ((i2c_dev->msg_err & BCM2835_I2C_S_ERR) &&
 188             (msg->flags & I2C_M_IGNORE_NAK))
 189                 return 0;
 190
 191         dev_err(i2c_dev->dev, "i2c transfer failed: %x\n", i2c_dev->msg_err);
 192
 193         if (i2c_dev->msg_err & BCM2835_I2C_S_ERR)
 194                 return -EREMOTEIO;
 195         else
 196                 return -EIO;
 197 }
 198
 199 static int bcm2835_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 200                             int num)
 201 {
 202         struct bcm2835_i2c_dev *i2c_dev = i2c_get_adapdata(adap);
 203         int i;
 204         int ret = 0;
 205
 206         for (i = 0; i < num; i++) {
 207                 ret = bcm2835_i2c_xfer_msg(i2c_dev, &msgs[i]);
 208                 if (ret)
 209                         break;
 210         }
 211
 212         return ret ?: i;
 213 }
 214
 215 static u32 bcm2835_i2c_func(struct i2c_adapter *adap)
 216 {
 217         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 218 }
 219
 220 static const struct i2c_algorithm bcm2835_i2c_algo = {
 221         .master_xfer    = bcm2835_i2c_xfer,
 222         .functionality  = bcm2835_i2c_func,
 223 };
 224
 225 /*
 226  * This HW was reported to have problems with clock stretching:
 227  * http://www.advamation.com/knowhow/raspberrypi/rpi-i2c-bug.html
 228  * https://www.raspberrypi.org/forums/viewtopic.php?p=146272
 229  */
 230 static const struct i2c_adapter_quirks bcm2835_i2c_quirks = {
 231         .flags = I2C_AQ_NO_CLK_STRETCH,
 232 };
 233
 234 static int bcm2835_i2c_probe(struct platform_device *pdev)
 235 {
 236         struct bcm2835_i2c_dev *i2c_dev;
 237         struct resource *mem, *irq;
 238         u32 bus_clk_rate, divider;
 239         int ret;
 240         struct i2c_adapter *adap;
 241
 242         i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
 243         if (!i2c_dev)
 244                 return -ENOMEM;
 245         platform_set_drvdata(pdev, i2c_dev);
 246         i2c_dev->dev = &pdev->dev;
 247         init_completion(&i2c_dev->completion);
 248
 249         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 250         i2c_dev->regs = devm_ioremap_resource(&pdev->dev, mem);
 251         if (IS_ERR(i2c_dev->regs))
 252                 return PTR_ERR(i2c_dev->regs);
 253
 254         i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
 255         if (IS_ERR(i2c_dev->clk)) {
 256                 if (PTR_ERR(i2c_dev->clk) != -EPROBE_DEFER)
 257                         dev_err(&pdev->dev, "Could not get clock\n");
 258                 return PTR_ERR(i2c_dev->clk);
 259         }
 260
 261         ret = of_property_read_u32(pdev->dev.of_node, "clock-frequency",
 262                                    &bus_clk_rate);
 263         if (ret < 0) {
 264                 dev_warn(&pdev->dev,
 265                          "Could not read clock-frequency property\n");
 266                 bus_clk_rate = 100000;
 267         }
 268
 269         divider = DIV_ROUND_UP(clk_get_rate(i2c_dev->clk), bus_clk_rate);
 270         /*
 271          * Per the datasheet, the register is always interpreted as an even
 272          * number, by rounding down. In other words, the LSB is ignored. So,
 273          * if the LSB is set, increment the divider to avoid any issue.
 274          */
 275         if (divider & 1)
 276                 divider++;
 277         if ((divider < BCM2835_I2C_CDIV_MIN) ||
 278             (divider > BCM2835_I2C_CDIV_MAX)) {
 279                 dev_err(&pdev->dev, "Invalid clock-frequency\n");
 280                 return -ENODEV;
 281         }
 282         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_DIV, divider);
 283
 284         irq = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 285         if (!irq) {
 286                 dev_err(&pdev->dev, "No IRQ resource\n");
 287                 return -ENODEV;
 288         }
 289         i2c_dev->irq = irq->start;
 290
 291         ret = request_irq(i2c_dev->irq, bcm2835_i2c_isr, IRQF_SHARED,
 292                           dev_name(&pdev->dev), i2c_dev);
 293         if (ret) {
 294                 dev_err(&pdev->dev, "Could not request IRQ\n");
 295                 return -ENODEV;
 296         }
 297
 298         adap = &i2c_dev->adapter;
 299         i2c_set_adapdata(adap, i2c_dev);
 300         adap->owner = THIS_MODULE;
 301         adap->class = I2C_CLASS_DEPRECATED;
 302         strlcpy(adap->name, "bcm2835 I2C adapter", sizeof(adap->name));
 303         adap->algo = &bcm2835_i2c_algo;
 304         adap->dev.parent = &pdev->dev;
 305         adap->dev.of_node = pdev->dev.of_node;
 306         adap->quirks = &bcm2835_i2c_quirks;
 307
 308         bcm2835_i2c_writel(i2c_dev, BCM2835_I2C_C, 0);
 309
 310         ret = i2c_add_adapter(adap);
 311         if (ret)
 312                 free_irq(i2c_dev->irq, i2c_dev);
 313
 314         return ret;
 315 }
 316
 317 static int bcm2835_i2c_remove(struct platform_device *pdev)
 318 {
 319         struct bcm2835_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
 320
 321         free_irq(i2c_dev->irq, i2c_dev);
 322         i2c_del_adapter(&i2c_dev->adapter);
 323
 324         return 0;
 325 }
 326
 327 static const struct of_device_id bcm2835_i2c_of_match[] = {
 328         { .compatible = "brcm,bcm2835-i2c" },
 329         {},
 330 };
 331 MODULE_DEVICE_TABLE(of, bcm2835_i2c_of_match);
 332
 333 static struct platform_driver bcm2835_i2c_driver = {
 334         .probe          = bcm2835_i2c_probe,
 335         .remove         = bcm2835_i2c_remove,
 336         .driver         = {
 337                 .name   = "i2c-bcm2835",
 338                 .of_match_table = bcm2835_i2c_of_match,
 339         },
 340 };
 341 module_platform_driver(bcm2835_i2c_driver);
 342
 343 MODULE_AUTHOR("Stephen Warren <swarren@wwwdotorg.org>");
 344 MODULE_DESCRIPTION("BCM2835 I2C bus adapter");
 345 MODULE_LICENSE("GPL v2");
 346 MODULE_ALIAS("platform:i2c-bcm2835");